refactor: introduce and use safe_localtime()

include/dwarfs/util.h

@@ -83,4 +83,6 @@ int get_current_umask();
 
 void install_signal_handlers();
 
+std::tm safe_localtime(std::time_t t);
+
 } // namespace dwarfs

src/history.cpp

@@ -37,6 +37,7 @@
 #include <dwarfs/history.h>
 #include <dwarfs/library_dependencies.h>
 #include <dwarfs/malloc_byte_buffer.h>
+#include <dwarfs/util.h>
 #include <dwarfs/version.h>
 
 #include <dwarfs/gen-cpp2/history_types.h>
@@ -105,10 +106,9 @@ void history::dump(std::ostream& os) const {
     for (auto const& histent : *history_->entries()) {
       os << "  " << fmt::format("{:>{}}:", i++, iwidth);
 
-      if (histent.timestamp().has_value()) {
-        os << " "
-           << fmt::format("[{:%Y-%m-%d %H:%M:%S}]",
-                          fmt::localtime(histent.timestamp().value()));
+      if (auto ts = histent.timestamp(); ts.has_value()) {
+        os << " [" << fmt::format("{:%F %T}", safe_localtime(ts.value()))
+           << "]";
       }
 
       auto const& version = histent.version().value();
@@ -172,11 +172,10 @@ nlohmann::json history::as_json() const {
       }
     }
 
-    if (histent.timestamp().has_value()) {
+    if (auto ts = histent.timestamp(); ts.has_value()) {
       entry["timestamp"] = {
-          {"epoch", histent.timestamp().value()},
-          {"local", fmt::format("{:%Y-%m-%dT%H:%M:%S}",
-                                fmt::localtime(histent.timestamp().value()))},
+          {"epoch", ts.value()},
+          {"local", fmt::format("%FT%T", safe_localtime(ts.value()))},
       };
     }
 

src/reader/internal/metadata_v2.cpp

@@ -1335,8 +1335,7 @@ metadata_v2_data::info_as_json(fsinfo_options const& opts,
   }
 
   if (auto ts = meta_.create_timestamp()) {
-    info["created_on"] =
-        fmt::format("{:%Y-%m-%dT%H:%M:%S}", fmt::localtime(ts.value()));
+    info["created_on"] = fmt::format("{:%FT%T}", safe_localtime(ts.value()));
   }
 
   if (opts.features.has(fsinfo_feature::metadata_summary)) {
@@ -1468,11 +1467,8 @@ void metadata_v2_data::dump(
   }
 
   if (auto ts = meta_.create_timestamp()) {
-    time_t tp = *ts;
-    std::string str(32, '\0');
-    str.resize(
-        std::strftime(str.data(), str.size(), "%F %T", std::localtime(&tp)));
-    os << "created on: " << str << "\n";
+    os << "created on: " << fmt::format("{:%F %T}", safe_localtime(*ts))
+       << "\n";
   }
 
   if (opts.features.has(fsinfo_feature::metadata_summary)) {

src/util.cpp

@@ -556,4 +556,19 @@ void install_signal_handlers() {
 #endif
 }
 
+std::tm safe_localtime(std::time_t t) {
+  std::tm buf{};
+#ifdef _WIN32
+  if (auto r = ::localtime_s(&buf, &t); r != 0) {
+    DWARFS_THROW(runtime_error, fmt::format("localtime_s: error code {}", r));
+  }
+#else
+  if (!::localtime_r(&t, &buf)) {
+    DWARFS_THROW(runtime_error,
+                 fmt::format("localtime_r: error code {}", errno));
+  }
+#endif
+  return buf;
+}
+
 } // namespace dwarfs

test/tool_main_test.cpp

@@ -2631,16 +2631,17 @@ TEST(dwarfsck_test, list_files_verbose) {
 
   auto num_lines = std::count(out.begin(), out.end(), '\n');
   EXPECT_EQ(12, num_lines);
+  auto format_time = [](time_t t) {
+    return fmt::format("{:%F %H:%M}", safe_localtime(t));
+  };
 
   std::vector<std::string> expected_re{
-      fmt::format("drwxrwxrwx\\s+1000/100\\s+8\\s+{:%Y-%m-%d %H:%M}\\s*\n",
-                  fmt::localtime(2)),
-      fmt::format(
-          "-rw-------\\s+1337/  0\\s+{:L}\\s+{:%Y-%m-%d %H:%M}\\s+baz.pl\n",
-          23456, fmt::localtime(8002)),
-      fmt::format("lrwxrwxrwx\\s+1000/100\\s+16\\s+{:%Y-%m-%d "
-                  "%H:%M}\\s+somelink -> somedir/ipsum.py\n",
-                  fmt::localtime(2002)),
+      fmt::format("drwxrwxrwx\\s+1000/100\\s+8\\s+{}\\s*\n", format_time(2)),
+      fmt::format("-rw-------\\s+1337/  0\\s+{:L}\\s+{}\\s+baz.pl\n", 23456,
+                  format_time(8002)),
+      fmt::format("lrwxrwxrwx\\s+1000/100\\s+16\\s+{}\\s+somelink -> "
+                  "somedir/ipsum.py\n",
+                  format_time(2002)),
   };
 
   for (auto const& str : expected_re) {

tools/src/dwarfsck_main.cpp

@@ -103,10 +103,10 @@ void do_list_files(reader::filesystem_v2& fs, iolayer const& iol,
 
       auto st = fs.getattr(iv);
 
-      iol.out << fmt::format(
-          "{3} {4:{0}}/{5:{1}} {6:{2}L} {7:%Y-%m-%d %H:%M} {8}\n", uid_width,
-          gid_width, inode_size_width, iv.mode_string(), iv.getuid(),
-          iv.getgid(), st.size(), fmt::localtime(st.mtime()), name);
+      iol.out << fmt::format("{3} {4:{0}}/{5:{1}} {6:{2}L} {7:%F %H:%M} {8}\n",
+                             uid_width, gid_width, inode_size_width,
+                             iv.mode_string(), iv.getuid(), iv.getgid(),
+                             st.size(), safe_localtime(st.mtime()), name);
     } else if (!name.empty()) {
       iol.out << name << "\n";
     }